In industry, systems are required for driverless, mobile assembly and/or material transport units which can continue to operate 24 hours a day, 7 days a week without being connected to the power supply system. Normally, batteries are used as power supply units. However, these need to be recharged or replaced again and again at appropriate intervals. It is not possible for the industrial trucks to be used during this time.
It is known to use a method for operating an assembly facility with DTS of the type mentioned at the outset, in which the driverless, mobile assembly and/or material transport units have an energy storage device for providing the energy for the drive device, said energy storage device being in the form of a battery. In order to maintain usability over a relatively long period of time, the batteries need to have a high capacity, which necessitates the use of high-volume and heavy batteries. As soon as the state of charge of the batteries becomes critical, the assembly and/or material transport unit needs to be charged at a separate charging station and is no longer available for use purposes for a relatively long period of time.
The demands made by DTS users are therefore becoming greater and greater. A DTS should run 7 days a week, 24 hours a day. The charge times of from 5 to 6 hours for previous battery-operated DTS can no longer be maintained.
Furthermore, induction-guided energy systems have the disadvantage that the floor needs to be cut open, there is a poor energy efficiency and the entire application is very expensive and inflexible.
Electric vehicles are known, in which, in addition to a battery, a double-layer capacitor device, which is also referred to as a supercap or boostcap, is provided. The energy management is configured in this case such that the battery supplies the motor. The supercap is used for discharging the battery, for example when ascending a mountain, in order that an excessively high current does not flow and that the battery does not wear out prematurely. During operation in the generator mode, for example on downhill runs, the supercap is charged.
EP 0 475 106 A1 has described a driverless transport system with a driverless travel unit, wherein the travel unit is guided along a clearly defined travel route. Charging electrodes are provided at certain regions of the travel route, it being possible for said charging electrodes to be brought into contact, tangibly, with electrodes provided on the vehicle, with the result that the vehicle can be driven and, if appropriate, the battery provided on the vehicle can be charged.
US 2008/0277173 A1 discloses a charging system for vehicles, such as buses, for example, in which the vehicles have an energy storage system, which has two components, namely a double-layer capacitor device and a battery. The energy for the drive device of the vehicle is provided by the double-layer capacitors. These double-layer capacitors are charged automatically at certain charging stations. In the event of downhill travel or braking, the energy released thereby (the motor then operates as a generator) is used for charging the double-layer capacitors, wherein, as soon as the double-layer capacitor device is fully charged, this energy is passed on, via said double-layer capacitor device, to the battery in order to charge said battery.